Acoustic diaphragm and loud-speaker combination



April 8, 19300 A N. BALDWIN 1,753,979

ACOUSTIC DIAPHRAGM AND LOUD SPEAKER COMBINATION Filed Feb. l0, 1926 W INVENTOR Patented Apr... 8,. 193

STES

' NATHANIEL BALDWIN, OF EAST MILL CREEK, UTAH ACOUSTIC DIAPHRAGM AND LOUD-SPEAKER COMBINATION Application filed February 10, 1926. Serial No. 87,362.

The present invention appertains to acoustic diaphragms and particularly to that class in which large diaphragms are used without horns for loud speakers.

The principal object of the invention is to produce a diaphragm which is light, delicate, sensitive and highly eflicient.

T attain this and other objects by the mechanism illustrated in the accompanying drawm ing in which Fig. 1 is a section of the instrument showing the various working parts and Fig. 2 is a rear elevation.

In both figures numeral 1 designates the housing which may be made in the form of a cylinder. Numeral 2 designates a ring which is secured to the inner surface of the housing 1 and at its inner circumference is provided with a projecting flange 3 which forms a seat for the diaphragm. The diaphragm 4 made of paper or other like material has a double curvature or cuspidal shape in the middle portion and is adapted to be drawn tight in every direction by a force applied at the center by means of the cord loop 5.

The edge of the diaphragm is provided with a re-enforcing rim 6 made of a folded strip of nietal or other suitable material. The rim 6'is somewhat larger in diameter than the flange 3, and when the diaphragm is placed against the flange 3 and force is applied to the rim 6 to press the diaphragm against the flange the dia hragm will be put under tension. A suitab e force against the rim 6 and uniformly distributed around it is obtained. by means of an expansible ring 7 preferably a compressedspiral spring, which presses against an inclined surface 8 on one side of an annular groove formed in the inner wall of the housing 1 and against said rim. The housing may be conveniently made of sheet metal, in which case the groove will consist of an annular bead in the material.

The diaphragm as described may be used to produce sound as in a phonograph reproducer or telephone, or to receive sound as in a phonograph recorder or microphone. but as here illustrated it is used in a loud speaker in combination with other improvements described as follows Numeral 9 designates an electrically operated armature hung within the spool 10 upon the fulcrum 11, and polepieces 12, 12, surround thespool and act upon the armature at either end. A projection upon the end of the armature 9 receives the cord loop 5 which communicates the movements of the armature tothe diaphragm. Permanent horseshoe magnets 13, 13 contacting with and supporting'said polepieces are secured to a plate 14 which is mounted upon the cross bar 15 secured at both ends to the walls of the housmg 1.

A rectangular projection 16 formed upon the under side of the plate 14: fits into a 55 slideway in the crossbar 15 and a screw 17 and washer 18 hold the plate 14 in place. A spring 19 seated in the projection 16 holds it in contact with the screw 20'by means of which the combination of working parts can be moved to and fro and the tension on the diaphragm adjusted. The position of the armature between the polepieces is adjustable'by means of the screw 21 with tip 22 made of rubber or other suitable spongy material.

It will be seen that on account of the form of this diaphragm, when force is applied to the center the whole diaphragm will be put under tension in all directions and that it so- Will be forcefully responsive throughout to any variation in that force. I

The housing 1 may be mounted upon a base 23 of any deslred form.

I claim a5 1. A diaphragm having a cuspidal middle portion and a re-enforcing rim, a housing for said diaphragm, an annular seat for said diaphragm secured to said housing, an annular in lined surface 111 said housing, and an ex W pansibie ring pressing against said. inclined surface and against said rim and adapfied to put tension on said diaphragm by pressing against said seat.

2. In combination a diaphragm, an 0psrsting mechanism comprising an armature, an actuating coil disposed around said armature, means to move said mechanism and other means including a bsdy which has substantially no natural Vibration period for adjusting said armature in said csii,

NATHAIHEL BALDW INQ 

